Describe, step by step, how we can map the field of variable quantity

Following are the steps through which a field of variable quantity can be mapped:

Step I: Choose a temporary benchmark (TBM). It should be stationary and unalterable. Step II: Plot temporary reference points on the field with the TBM as the master reference point. Step III: Take measurements of the features and quantities like trees, rocks, buildings (if any), elevations, etc., present in the field from the temporary reference points. Step IV: Mark the quantities on the map based on the measurements obtained from the field. Explanation: To map a field of variable quantity, it becomes necessary to go step-by-step in order to bring accuracy in the process of mapping. The steps described above help in bringing precision in mapping and leave no room for error.

81 is a composite number